1. Field of the Invention
The present invention relates to media driving apparatuses used to read/write signals on a disc-shaped media such as a CD, a DVD or the like, and more particularly to a media driving apparatus which can precisely and easily adjust a tilt of an optical axis of an optical pickup with respect to signals recording surface of the media.
2. Description of the Related Art
In conventional, there has been known a CD player, a DVD player, a DVD recorder or the like as the media driving apparatus. The media driving apparatus is provided with a turn table for rotating the disc-shaped media, and an optical pickup moves along a radial direction of the media mounted on the turn table. The optical pickup irradiates a laser beam to signals (Pits and Lands) recorded on a surface (hereinafter referred as an information recording surface) of the media, and detects with or without the pit in correspondence to a magnitude of a reflected light amount from the media. Accordingly, in the case that a tilt of the laser beam is large with respect to the information recording surface of the media, the reflected light cannot be received, and a reading error of the pit is generated. Therefore, the media driving apparatus as mentioned above is provided with an adjusting mechanism for setting a tilt (an incident angle of an optical axis) of the laser beam irradiated from the optical pickup within an acceptable range.
With reference to FIGS. 1 and 2, an embodiment of the adjusting mechanism mentioned above will be described below. Reference symbol D denotes a disc-shaped media, reference symbol T denotes a turn table for rotating the media D, reference symbol P denotes an optical pickup, reference symbol R denotes a screw axis for moving the optical pickup P, reference symbol M denotes a motor for driving so as to rotate the screw axis R, and reference symbol G denotes a guide axis for guiding the optical pickup P, respectively. A tilt adjusting screw N and an elastic member S are provided in both end portions of the guide axis G so as to oppose to each other, and a tilt of the guide axis G is adjusted with respect to the information recording surface of the media D by rotating each of the screws N.
After combining the respective parts mentioned above with each other, a pair of guide axes G are arranged in parallel to the information recording surface of the media D mounted on the turn table T by operating the tilt adjusting screw N. Based on this operation, it is possible to prevent the pit reading error from being occurred by irradiating the laser beam perpendicularly from the optical pickup P to the information recording surface of the media D.
However, in the structure in which the optical pickup P is supported by a pair of guide axes G, since a large number of the parts are needed, therefore there has been a problem that it is hard to make the apparatus compact and inexpensive. Further, in the case that an engagement between a rack L provided in the optical pickup P and the screw axis R is deteriorated by changing the tilt of a pair of guide axes G with respect to the information recording surface of the media D, there is rarely a risk that the optical pickup P cannot move.
According to another conventional media driving apparatus structured such that both sides of the optical pickup are supported by the screw axis and the guide axis, and the tilt of the screw axis can be adjusted with respect to the information recording surface of the media (for example, Japanese Patent Application Laid-open No. H11-283253).
However, in the structure in which one side of the optical pickup is supported by the screw axis which is driven so as to rotate, the rotation of the screw axis is resisted by pressing the tilt adjusting screw to an outer peripheral surface of the screw axis. As a result, not only an overload is generated in a driving source, but also an outer peripheral surface of the screw axis and a leading end of the tilt adjusting screw worn by the rotation of the screw axis, whereby there is a problem that the tilt of the screw axis gradually becomes large with respect to the information recording surface of the media. As a result, the laser beam irradiated to the information recording surface of the media from the optical pickup is tilted. And with the tilt becomes larger than the acceptable range, the pit reading error is occurred.
Accordingly, in the related art mentioned above, a traverse base plate is mounted to a main base plate to which a guide axis (a first guide rail) or the like is mounted, via a C-shaped spring. A screw axis (a feed screw) and a motor (a driving source) are arranged on the traverse base plate, and a tilt of the screw axis is adjusted by operating the screws inserted to two positions of the traverse base plate.
However, since the traverse base plate is provided on the main base plate, it is hard to make the apparatus compact. In addition, since the tilt of the screw axis is indirectly adjusted via the traverse base plate, an accuracy of the parts is required. Further, in addition, it is hard to adjust the tilt of the optical axis of the optical pickup with respect to the information recording surface of the media at a high accuracy, and it is hard to obtain a high adjusting accuracy with respect to a deflection of the traverse base plate. This point is disadvantageous in the case that the recording density of the media such as a Compact Disk, a DVD, becomes higher.
The present invention is made by taking the circumstances mentioned above into consideration, and an object of the present invention is to provide a media driving apparatus which can accurately and easily execute a tilt adjustment of an optical axis of an optical pickup with respect to an information recording surface of a media while making the apparatus compact.